In an art of a transmit diversity, it is possible to improve robustness of communication by using an MIMO channel. At this time, a transmission signal is carefully designed as for both space and time, and a rank of an MIMO channel matrix is effectively used. For example, the transmission signal is made to be a quadrature signal, and thereby, it is possible to avoid an array interference generated by using a plurality of antennas. In this art, it is possible to generate an estimation of quadrature information in which the MIMO channel matrix becomes a full rank from a mixed signal of signals transmitted from a plurality of transmission antennas at a reception side. However, in a cellular network or the like covering a wide area, robustness for a deep fading is required at a cell boundary, and an application of only full diversity is not sufficient.
The present invention is one to further provide a gain due to the array interference of a system in addition to maintain a maximum diversity (to provide the MIMO matrix of full rank). This special gain is one which is obtained by carefully designing a transmission symbol transmitted from each of transmission antennas, and the array interference is positively used at the reception side.
In the art of the transmit diversity, the robustness of the communication in the MIMO channel is improved by using space-time block codes or the like. However, in such an art, it is limited to a coefficient of the diversity, and therefore, there is a problem in which a reception quality in a vicinity of a cell boundary and system performance are insufficient.